JPS5946540B2 - Fluoro rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cured fluororubber composition, and more particularly to a fluororubber composition containing a polyhydroxy aromatic compound as a crosslinking agent and a nitrogen-containing cyclic polyether as an accelerator.

A fluororubber, such as a rubbery copolymer of vinylidene fluoride and at least one other monomer, is cured using a polyhydroxy aromatic compound as a crosslinking agent;
It is known to provide cured fluororubber products with excellent heat resistance, oil resistance, solvent resistance, chemical resistance, etc.

Since this polyhydroxy aromatic compound generally has poor crosslinking reactivity, an appropriate accelerator is usually used in combination, for example, one selected from various nitrogen-containing or phosphorus-containing organic compounds is suitably used as the accelerator. . However, these accelerators have the disadvantage that their usage is limited because they have an undesirable effect on the physical properties of the cured fluororubber product. On the other hand, cyclic polyethers are known as accelerators that have relatively little adverse effect on cured fluorine rubber products (see Japanese Patent Publication No. 47-51812).

However, although this cyclic polyether has the effect of increasing the crosslinking reactivity of polyhydroxy aromatic compounds, it is still not fully satisfactory from a commercial standpoint. In view of the drawbacks of the various accelerators mentioned above, the present inventors have proposed that when using a polyhydroxy aromatic compound as a crosslinking agent,
Minimize the negative impact on the fluoro rubber cured product as much as possible.
Moreover, as a result of repeated studies on compounds that can sufficiently function as accelerators, it was discovered that the objective could be achieved with a certain type of nitrogen-containing cyclic polyether, and the present invention was completed.

That is, the gist of the present invention is that one CH2 is present in the polymer molecular chain.
A fluororubber containing -CF2- units, a crosslinking agent made of a polyhydroxy aromatic compound, an accelerator made of a nitrogen-containing cyclic polyether having at least one nitrogen atom in its skeleton as described below, and a divalent A fluororubber composition containing a metal oxide or its hydroxide. According to the fluororubber composition of the present invention, the problems of the prior art described above are solved, and in particular, the crosslinking reactivity of the polyhydroxy aromatic compound is greatly improved compared to the case of using a conventional cyclic polyether. Improved.

Therefore, when using conventional cyclic polyethers, metal salts (e.g., sodium salts) of weak acids such as stearic acid, benzoic acid, chlorophenol, thiophenol, etc. are always required to obtain practical crosslinking reactivity. However, when using a nitrogen-containing cyclic polyether as in the present invention, a commercially valuable curing rate can be achieved without using a weak acid metal salt that has a large negative effect on compression set. A cured product of fluorine rubber can be obtained.
In addition, compositions using conventional cyclic polyethers do not give desirable cured products, and therefore do not show good results in terms of heated air aging behavior. With the composition, a preferable final cured product can be obtained and such problems are less likely to occur. The fluororubber used in the present invention is a fluorinated rubbery copolymer,
Preferred fluororubbers include vinylidene fluoride, hexafluoropropene, pentafluoropropene,
trifluoroethylene, trifluorochloroethylene,
One or more rubbery copolymers such as tetrafluoroethylene, vinyl fluoride, perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether), perfluoro(propyl vinyl ether),
Examples include a rubbery copolymer of tetrafluoroethylene and propylene, a rubbery copolymer of ethylene and hexafluoropropylene, and the like.

Among these, binary copolymers of vinylidene fluoride and hexafluoropropene and terpolymers of vinylidene fluoride, tetrafluoroethylene and hexafluoropropene are particularly preferably used. Polyhydroxy aromatic compounds include benzene, biphenyl, naphthalene, etc. which are substituted with two or more hydroxyl groups, and specific examples include hydroquinone, catechol, resorcinol, 2-methylhydroquinone, 2-5
-dimethylhydroquinone, 2-t-butylhydroquinone, 2-methylresorcin, 5-methylresorcin, 1.
3,5-trihydroxybenzene, 1,7-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 2.
7-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,2-bis(4-hydroxyphenyl)propane [bisphenol A], 2,2-bis(4-hydroxyphenyl)perfluoropropane [bisphenol] AF], 2.2-bis(4-hydroxyphenyl)butane [bisphenol B], 2.2-bis(4-hydroxyphenyl)tetrafluorodichloropropane, 3.
3', 5, 5'-tetrachlorbisphenol Al3.
3', 5, 5'-tetrabromobisphenol Al4.
4'-dihydroxydiphenyl, 4,4'-dihydroxydiphenyl ether, 4,4-bis(4-hydroxyphenyl)valeric acid, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl Examples include ketone, tri(4-hydroxyphenyl)methane, and the like. Among these, hydroquinone, bisphenol A, bisphenol A, bisphenol B, and the like are particularly preferred. These aromatic polyols can also be used in the form of salts with alkali metals or alkaline earth metals. The nitrogen-containing cyclic polyether used as a promoter includes a nitrogen-containing cyclic polyether having at least one nitrogen atom in the skeleton, and has the general formula: [wherein m is the same or different integer of 1 to 5; n is the same or different integer of O to 1; R represents a group represented by the formula: (wherein, X is a hydrogen atom or an alkyl group);

] Examples include cyclic polyethers represented by the following.

Among these polyethers, common ones are 4.
7, 13, 16, 21, 24-hexaoxa-1, 10
-Diazabicyclo [8,8,8] Hexacosane (Cryptofix 222), 4,7,13,16,21-Pentaoxa-1,10-Diazabicyclo [8,8●5]
Trichosan (Cryptofix 221), 4.7.1
3,18-tetraoxa-1,10-diazabicyclo [
8.5.5] Eikosan (Cryptofix 211)
, 1,13-bis-(8-quinolyl)-1,4,7,1
0,13-Pentaoxatridecane (Cryptofix 5), 5,6-Pensor 4,7,13,16,21.
24-hexaoxa-1,10-diazabicyclo[8.
8.8] Hexacosane (Cryptofix 222B)
, 5-decyl-4.7.13.16.21.24-hexaoxa-1.10-diazabicyclo[8.8.8]hexacosane (Cryptofix 222D), 1.7.
10-trioxa-4,13-diazacyclopentadecane (Cryptofix 21), 1,7,10,16-
Tetraoxa-4,13-diazacyclooctadecane (
Cryptofix 22), 5, 6, 14, 15-dipenso 4, 7, 13, 16, 21, 24-hexaoxa-1, 10-diazabicyclo [8, 8, 8] hexacosane (Crypto Fix 222BB), dibenzo Pyridino-18-Crown-6, etc. (Cryptofix is a product name of Talc Corporation). Furthermore, a divalent metal oxide or its hydroxide is desirably added to the composition of the present invention, and is used mainly for fixing acidic substances generated by the crosslinking reaction. As the metal oxide or hydroxide, alkaline earth metal oxides or hydroxides are usually used alone or as a mixture of two or more, preferably oxides of magnesium, calcium, zinc, etc., or hydroxides of alkaline earth metals. oxides are used. The ratio of polyhydroxy aromatic compound and nitrogen-containing cyclic polyether to fluoro rubber is usually 100% of fluorocarbon rubber.
(parts by weight, hereinafter the same), the former is used in a ratio of 0.5 to 5 parts, preferably 1 to 2 parts, and the latter is used in a ratio of 0.3 to 10 parts, preferably 0.3 to 2 parts. Furthermore, the amount of metal oxide or its hydroxide is 1 to 20 parts per 100 parts of fluororubber.
parts, preferably 2 to 15 parts.

The composition of the present invention may also contain conventional additives such as plasticizers, fillers, reinforcing agents, and colorants, if necessary.

Vulcanization of the composition of the present invention is carried out according to the usual fluoro rubber vulcanization conditions. For example, after roll-kneading the composition, the composition is put into a mold and heated at 150 to 200°C to form a molded product. Primary vulcanization is carried out by holding under a pressure of 35k9 per unit area (CrlL) for 10 to 30 minutes, and then at 200 to 260'C.
Secondary vulcanization is carried out by maintaining the mixture in a furnace for 16 to 24 hours.

Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Examples 1 to 4 and Comparative Examples 1 to 4 Vinylidene fluoride (VDF) as rubber
/ Hexafluoropropene (HF) copolymer was blended with various components in the proportions shown in Table 1, and after uniformly kneading with a rubber roll, each of the resulting blended doughs was dispensed into molds, and 1
20 minutes at 70℃*? Perform press vulcanization, then 23
Vulcanize in oven for 22 hours at 0°C.

The normal physical properties of the vulcanized rubber were measured for each vulcanized sample according to the method specified in JIS K63Ol. The results are shown in Table 2. In addition, the vulcanization test was carried out using JSR type Cyulastome manufactured by Japan Synthetic Rubber Co., Ltd., mold chamber No. 11, vibration frequency 6 cpm, swing width ±3 degrees, and temperature 170°C.
It was conducted under the following conditions. The test results are shown in Table 2. The following is understood from the above results.

That is, in Comparative Example 3, a satisfactory vulcanized rubber could not be obtained even after vulcanization at 170° C. for 30 minutes, and there was a problem in vulcanizability. By using this in combination with sodium stearate, the vulcanizability and physical property values of the vulcanized rubber shown in Comparative Examples 1 and 2 can be obtained. However, when comparing and contrasting the results of Comparative Examples 1 and 2 with the results of Examples 1 and 4, the latter is superior in vulcanizability, elongation of vulcanized rubber, and compression set value. It is clear that the difference is of sufficient significance in the art.

Furthermore, regarding the amount of accelerator used, compared to Comparative Examples 1 to 3, it was smaller in Examples 1.3 and 4, and approximately the same amount in Example 2. It is shown that the ether provides a more favorable effect in a smaller amount than conventional cyclic polyethers.

Claims (1)

[Claims] 1. Fluororubber containing -CH_2-CF_2- units in the polymer molecular chain, crosslinking agent made of polyhydroxy aromatic compound, general formula: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ ▲Mathematical formulas, There are chemical formulas, tables, etc. ▼ ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [In the formula, m is an integer from 1 to 5 that is the same or different; n is the same or different Different integers from 0 to 1; R is a formula: ▲ Numerical formula, chemical formula,
There are tables, etc. ▼, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼
Or ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However,
represents a group represented by a hydrogen atom or an alkyl group. A fluororubber composition comprising a promoter made of a nitrogen-containing cyclic polyether represented by the following formula and a divalent metal oxide or a hydroxide thereof. 2. The fluororubber composition according to claim 1, wherein the polyhydroxy aromatic compound is a dihydroxy aromatic compound.